Improvements relating to print wheel setting mechanisms



Dec 8, 1970 A. HOLDSWORTH IMPROVEMENTS RELATING TO PRINT WHEEL SETTING MECHANISMS Filed Aug. 15, 1968 United States Patent 3,545,291 IMPROVEMENTS RELATING TO PRINT WHEEL SETTING MECHANISMS Alan Holdsworth, Essex County, England, assignor to The Plessey Company Limited, Ilford, England, a British company Filed Aug. 15, 1968, Ser. No. 752,838 Claims priority, application Great Britain, Aug. 16, 1967, 37,759/ 67 Int. Cl. F16h 27/10 US. Cl. 74-1255 Claims ABSTRACT OF THE DISCLOSURE A print wheel setting mechanism comprising a print wheel having teeth bearing print type, which is driven through a clutch arrangement from a driving shaft so that when a print wheel tooth bearing a selected print type character is selected by stopping the print wheel at a particular angular position, continued rotation of the driving shaft is facilitated.

This invention relates to print wheel setting mechanisms.

According to the present invention a print wheel setting mechanism comprises a print wheel bearing print type characters on the circumferential faces of teeth of uniform pitch which are spaced around its periphery, a shaft on which the print wheel is journalled for rotation, an annular toothed setting wheel member, the teeth of which are intermeshed for driving purposes with the teeth of the print wheel, a hub member on which said setting wheel member is journalled, a spring loaded pawl pivoted on one of said members, catch means in the other of said members with which the spring loaded pawl engages when a predetermined angular relationship between the said members obtains so as to couple the members for driving purposes, a driving spindle on which the hub is fitted and a setting latch which in use of the mechanism is operable for causing the print wheel with which it is operatively associated to be restrained when the print wheel assumes a predetermined angular position, the pawl being adapted to disengage from said catch means when the print wheel is restrained, to permit further rotation of the driving spindle.

The setting wheel may be restrained by a setting latch which is adapted to engage at least one tooth of the setting wheel to prevent it from further rotation when the print wheel has reached a selected position. The drive to the hub member may be reversed for re-setting purposes, the hub member being arranged to rotate until the engagement part of the pawl once again co-operates with a notch in the setting wheel which is then driven by the hub member to a datum position. The pawl and the notch are so positionally related and constructed that disengagement of the pawl when the hub member is driven in this reverse direction is strongly resisted.

A particular advantage of the print-wheel setting mechanism according to the invention is that the setting wheel and the hub which incorporates the clutch mechanism, may be compactly fabricated so as to have a width (i.e. axial length) approximately the same as the width of the print wheel. This feature of compactness enables a number of print wheels each with its own clutch mechanism to be assembled side by side for the purposes of printing a line of selected characters. With an arrangement of this kind the hubs of the several clutch mechanisms are carried on a single shaft to which they are fixed. The shaft may then be rotated in one direction for setting purposes, individual print wheels being set to respective selected characters and then rotated in an opposite direction for resetting all the print wheels to a datum position. The datum position may conveniently be defined by a stop or projection fitted at the same angular position to each setting wheel, each stop being arranged to engage one of a number of fingers which are interdigitated with the setting wheels to define a stop comb.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings, in which corresponding parts of the several figures bear the same numerical designations, and in which FIG. 1 is an elevation of part of a print wheel setting mechanism,

FIG. 2 is a similar elevation of the mechanism shown in FIG. 1 but in a different operational position, and

FIG. 3 is a sectional end elevation of parts of a plurality of similar print wheel mechanisms each corresponding substantially with the mechanism of FIG. 1.

Referring to FIG. 1, a print wheel 1 journalled on a spindle 2 has disposed around its periphery elements of uniform pitch (not shown) carrying print type and separated from each other by axial grooves to form teeth which are intermeshed for driving purposes with teeth 3 of a generally annular setting wheel 4. The setting wheel 4 is mounted for rotation on a hub 5 which is secured to a driving shaft 6 extending parallel to the spindle 2. On one side of the hub 5' a pawl 7 is pivoted on a pin 8. A tooth-shaped portion 9 on one end of the pawl 7 is urged by a wire spring 10, acting on the other end of the pawl 7, against a bearing surface on the inside of the setting wheel 4 so as to engage when the setting wheel assumes a particular angular position, a notch 11 formed in the bearing surface. The wire spring 10 is substantially semicircular and is bent at each end to engage notches 12 and .13 provided respectively in an annular flange 14 which forms the centre portion of the hub and on the said other end of the pawl 7. In FIG. 1 the tooth-shaped portion 9 of the pawl 7 is shown engaged with the notch 11, and having driven the setting wheel 4 in an anti-clockwise direction until a zero or datum position is arrived at. At the datum position further anti-clockwise rotation of the setting wheel 4 is prevented by a stop 15 which engages one finger 16 of a stop comb (not fully shown). Referring to FIG. 2, for print-wheel setting purposes the hub 5 is rotated in a clockwise direction until a selected print type character reaches printing position. A setting latch 16' is then caused to engage a tooth gap of the setting wheel to prevent it from rotating further. The hub 5 however continues to rotate, causing the pawl 7 to ride out of the notch 11 in the setting-wheel bearing surface. For resetting purposes the drive direction is reversed and the setting latch is withdrawn. The hub then rotates initially independently of the setting wheel 4 in an anti-clockwise direction until the pawl once again engages the notch to return the setting wheel 4 to the datum position. As shown in FIG. 3 the width of the setting wheel 4 and hub assembly is much the same as the width of the print wheel 1. This enables any number of similar print wheels, each with their associated similar clutch mechanisms, to be assembled side by side, four being shown in FIG. 3, the hubs associated with each print wheel being mounted on a common driving shaft. With this arrangement, the shaft 6 may be rotated in a clockwise direction from the datum position, whereat a stop on each print wheel is arranged to engage a separate finger of the stop comb, the fingers of which are interdigitated between adjacent print wheels, each setting wheel being stopped by its own setting latch at a position selected in accordance with the type setting of a required character.

What I claim is:

.1. A print wheel setting mechanism comprising a print wheel bearing print type characters on the circumferential faces of teeth of uniform pitch which are spaced around its periphery, a shaft on which the print wheel is journalled for rotation, an annular toothed setting wheel member, the teeth ,of which are, intermeshed for driving purposes with the teeth of the print wheel, a hub member on which said setting wheel member is journalled, a spring loaded pawl pivoted on one of said members, catch means in the other of said members with which the spring loaded pawl engages when a predetermined angular relationship between the said members obtains so as to couple the members for driving purposes a driving spindle on which the hub is fitted and a setting latch which in use of the mechanism is operable for causing the print wheel with which it is operatively associated to be restrained when the print wheel assumes a predetermined angular position, the pawl being adapted to disengage from said catch means when the print wheel is restrained to permit further rotation of the driving spindle.

2. A print wheel setting mechanism as claimed in claim 1, comprising a plurality of print wheels each bearing print type characters on the circumferential faces of teeth of uniform pitch which are spaced around its periphery, a shaft on which each print wheel is journalled for rotation independently of the others, a plurality of generally annular toothed setting wheel members one for each print wheel, the teeth of the setting wheel members being intermeshed for driving purposes with the teeth of the print Wheels, a plurality of hub members one for each setting wheel member on which said setting wheel members are journalled, a plurality of spring loaded pawls pivoted one on each of said hub members, a plurality of catch means one in each of the setting wheel members with each of which an associated spring loaded pawl engages when a predetermined angular relationship obtains between the setting wheel member and its associated hub member, a driving spindle on which the hubs are fitted side-by-side, and a plurality of setting latches one for each print wheel each of which in use of the mechanism is operable for causing a print wheel with which it is operatively associated to be restrained when the print wheel assumes a predetermined angular position, the pawl being adapted to disengage from said catch means when its associated print wheel is restrained to permit further rotatiOn of the spindle.

3. A print wheel setting mechanism as claimed in claim 2, wherein the catch means comprises a notch formed in an inside circumferential surface of the annular setting wheel.

4. A print wheel setting mechanism as claimed in claim 3 wherein the latch is adapted to engage between teeth of the setting wheel, to restrain the print wheel.

5. A print wheel setting mechanism as claimed in claim 4 including a stop comb the fingers of which are interdigitated between the setting wheels and stop projections fitted to each setting wheel at the same angular position which engage with an associated finger of the stop comb for resetting purposes.

References Cited 25 UNITED STATES PATENTS 2,368,892 2/1945 Skoog 192-28 2,938,613 5/1960 Williams 192-43.1 2,989,160 6/1961 Woodrufl 192-12 30 3,142,202 7/1964 Miihlbeyer 192-43.l 3,327,825 6/1967 Farm 192-12 3,376,963 4/1968 Schaefer 192-12 WESLEY S. RATLIFF, JR., Primary Examiner 5 US. 01. X.R; 

